How to Create Product Variations Programmatically Using Taxonomy Attributes

I am struggling to create product variations programmatically. I wrote a script that creates WooCommerce products based on information from an API call. Everything works except for one issue regarding product variation attributes.

The problem I am facing is that when my variations are created, the attributes are not assigned, like so:

My desired outcome is for the attributes to be populated. I am assigning taxonomy attributes to the parent product and their values are showing up just fine, like so:

But when using this code to set attributes for my variation:

// set attributes
// $pa_format_term->term_id = integer; ID of term
// $pa_condition_term->term_id = integer; ID of term
$variation->set_attributes( 
    array( 
	'pa_format' => $pa_format_term->term_id,
	'pa_condition' => $pa_condition_term->term_id
    )
);

The problem where the attributes are not assigned to the variation persists. When I click to edit the WooCommerce product after my full script runs, a popup message is displayed that says, “Adding attributes failed,” which I’m assuming pertains to my issue.

I have tried everything I know of, read dozens of forum posts, pages, etc., and still can’t get this to work. I have tried using the term ‘name’ instead of the ID, which neither works for me.

Here is my full function for reference:

// Create a new product action
add_action( 'init', 'create_new_woocommerce_product');
function create_new_woocommerce_product() {
				
	global $woo_product_meta;
				
	// Download featured image				
	$image_data = @file_get_contents($woo_product_meta['image']);
	if($image_data) {
		$filename = basename($woo_product_meta['image']);
		$upload_file = wp_upload_bits($filename, null, $image_data);
		if (!$upload_file['error']) {
			$wp_filetype = wp_check_filetype($filename, null);
			$attachment = array(
				'post_mime_type' => $wp_filetype['type'],
				'post_title' => sanitize_file_name($filename),
				'post_content' => '',
				'post_status' => 'inherit'
			);
			$attachment_id = wp_insert_attachment( $attachment, $upload_file['file']);
			if (!is_wp_error($attachment_id)) {
				require_once(ABSPATH . "wp-admin" . '/includes/image.php');
				$attachment_data = wp_generate_attachment_metadata( $attachment_id, $upload_file['file'] );
				wp_update_attachment_metadata( $attachment_id,  $attachment_data );
			}
		}
	}

	// Create a new variable product
	$product = new WC_Product_Variable();
				
	// set title
	$product->set_name( $woo_product_meta['title'] );
				
	// set tags if they exist
	$tag_ids = array_map(
		function ($subject) {
			// remove unwanted symbols in tags
			$subject_str = str_replace(array(',', '&', '+', '-', '--', '=', ':', '.', '/', '\\', '@', '#', '$', '%', '^', '*', '(', ')', '[', ']', '{', '}', '\'', '"'), array(' ', ' and ', ' and ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' '), $subject);
			// remove multiple spaces in a row if found
			$subject_str = preg_replace('/\s+/', ' ', $subject_str);
			// convert tags to lowercase
			$subject_str = strtolower($subject_str);
			$term = get_term_by('name', $subject_str, 'product_tag');
			// if term exists
			if ( $term instanceof WP_Term ) {
				return (int) $term->term_id;
			}
			// if term doesn't exist
			else {
				if ( $subject_str !== '' ) {
					wp_create_term($subject_str, 'product_tag');
					// get new tag and set var
					$new_tag = get_term_by('name', $subject_str, 'product_tag');

					if ($new_tag instanceof WP_Term) {
						// set var to id val of tag
						return (int) $new_tag->term_id;
					} else {
						echo 'Notice: "' . $subject_str . '" was not created. Another tag exists that is too similar.';
					}
				} else {
					echo 'Notice: a tag input was blank and was skipped; cannot create a blank tag.';
				}
			}
		},
		$woo_product_meta['subjects']
	);				
	$product->set_tag_ids( $tag_ids );

	// Set featured image
	$product->set_image_id($attachment_id);
				
	// save progress
	$product->save();
				
	// set author(s)
	if ( isset($woo_product_meta['author']) ) {
		foreach ( $woo_product_meta['author'] as $author ) {
			// Check if there is a ',' in the author name
			if ( strpos($author, ',') !== false ) {
				// Get the last name
				$woo_meta_author_last_name = substr($author, 0, strpos($author, ','));
				// Set the full author name by swapping the first name and last name and removing the comma
				$woo_meta_author_full_name = substr($author, (strpos($author, ',') + 1)) . " " . $woo_meta_author_last_name; 
			} else {
				// Set the full name
				$woo_meta_author_full_name = $author;
				// Get the last word and set it as the last name
				$woo_meta_author_last_name = substr(strrchr($author, " "), 1); 
			}

			// Check if the authors taxonomy exists
			if ( term_exists( $woo_meta_author_full_name, 'authors' ) ) {
				// Assign the existing taxonomy item to the product
				wp_set_object_terms( $product->get_id(), $woo_meta_author_full_name, 'authors', true );
				// save progress
				$product->save();
			} else {
				// Create a new taxonomy item and assign it to the product
				wp_insert_term( $woo_meta_author_full_name, 'authors', array( 'slug' => sanitize_title( $woo_meta_author_full_name ) ) );
				wp_set_object_terms( $product->get_id(), $woo_meta_author_full_name, 'authors', true );
				// save progress
				$product->save();
			}

		}
	}
				
	// Set product attributes
	$attributes = array();

	// add the format attribute
	$attribute = new WC_Product_Attribute();
	$attribute->set_id( wc_attribute_taxonomy_id_by_name( 'pa_format' ) );
	$attribute->set_name( 'pa_format' );
	// see if current format attribute exists and set as var
	$pa_format_term = get_term_by('name', $woo_product_meta['format'], 'pa_format');
	if(!$pa_format_term){
		// create new pa_format term 
		wp_insert_term(
			$woo_product_meta['format'], // the term 
			'pa_format' // the taxonomy
		);
		$pa_format_term = get_term_by('name', $woo_product_meta['format'], 'pa_format');
		echo 'Created new term for pa_format: ' . $pa_format_term->name;
	} else {
		echo 'Existing pa_format term detected: ' . $pa_format_term->name;
	}
	$attribute->set_options( array( $pa_format_term->term_id ) );
	$attribute->set_position( 0 );
	$attribute->set_visible( true );
	$attribute->set_variation( true );
	$attribute->is_taxonomy( true );
	$attributes[] = $attribute;
				
	// add the condition attribute
	$attribute = new WC_Product_Attribute();
	$attribute->set_id( wc_attribute_taxonomy_id_by_name( 'pa_condition' ) );
	$attribute->set_name( 'pa_condition' );
	// see if current condition attribute exists and set as var
	$pa_condition_term = get_term_by('name', $woo_product_meta['condition'], 'pa_condition');
	if(!$pa_condition_term){
		// create new pa_format term 
		wp_insert_term(
			$woo_product_meta['condition'], // the term 
			'pa_condition' // the taxonomy
		);
		$pa_condition_term = get_term_by('name', $woo_product_meta['condition'], 'pa_condition');
		echo 'Created new term for pa_condition: ' . $pa_condition_term->name;
	} else {
		echo 'Existing pa_condition term detected: ' . $pa_condition_term->name;
	}
	$attribute->set_options( array( $pa_condition_term->term_id ) );
	$attribute->set_position( 1 );
	$attribute->set_visible( true );
	$attribute->set_variation( true );
	$attribute->is_taxonomy( true );
	$attributes[] = $attribute;
				
	$product->set_attributes( $attributes );
				
	// save the changes and go on
	$product->save();
				
	// create product variation
	$variation = new WC_Product_Variation();
	$variation->set_parent_id( $product->get_id() );
	$variation->set_regular_price( $woo_product_meta['price'] );
	
	$variation->save();
	
	// set attributes
	$variation->set_attributes( 
		array( 
			'pa_format' => $pa_format_term->term_id,
			'pa_condition' => $pa_condition_term->term_id
		)
	);
				
	$variation->save();
	
	// echo variation data for debugging purposes
	$variation_data = $variation->get_data();
	echo '<pre>'; 
	print_r($variation_data);
	echo '</pre>';
				
	$variation->set_image_id( $attachment_id );
	$variation->set_description( $woo_product_meta['description'] );
				
	$variation->set_sku( $woo_product_meta['isbn13'] );
	$variation->set_manage_stock( true );
	$variation->set_stock_quantity( 0 );
	$variation->set_backorders( 'notify' ); // 'yes', 'no' or 'notify'
	$variation->save();

	// Set the custom fields on the variation
	$variation_id = $variation->get_id();				
	$variation->update_meta_data('_isbn10_field', sanitize_text_field( $woo_product_meta['isbn10'] ) );
	$variation->update_meta_data('_isbn13_field', sanitize_text_field( $woo_product_meta['isbn13'] ) );
	$variation->update_meta_data('_language_field', sanitize_text_field( $woo_product_meta['language'] ) );
	$variation->update_meta_data('_release_field', sanitize_text_field( $woo_product_meta['date'] ) );
	$variation->update_meta_data('_publisher_field', sanitize_text_field( $woo_product_meta['publisher'] ) );
	$variation->update_meta_data('_length_field', sanitize_text_field( $woo_product_meta['length'] ) );
				
	// Save the variation  
	$variation->save();
				
	// Save the product
	$product->save();
				
	// show success message
	echo '<div>Successfully imported: ' . $woo_product_meta['title'] . '<div>';
	do_action( 'create_new_woocommerce_product' );
}

Please help me resolve this issue and let me know what other code snippets and information you might need. Thank you in advance!

Specifications:

• PHP 8.0.29
• WordPress 6.2.2
• WooCommerce 7.8.0